1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to apparatus and methods for delivering a plurality of separate luminal prostheses within a body lumen, such as a blood vessel.
Coronary artery disease is the leading cause of death and morbidity in the United States and Western society. In particular, atherosclerosis in the coronary arteries can cause myocardial infarction, commonly referred to as a heart attack, which can be immediately fatal or, even if survived, can cause damage to the heart which can incapacitate the patient.
While coronary artery bypass surgery can be an effective treatment for stenosed arteries resulting from atherosclerosis or other causes, it is a highly invasive procedure which is also expensive and which requires substantial hospital and recovery time. Percutaneous transluminal angioplasty, commonly referred to as balloon angioplasty, is less invasive, less traumatic, and significantly less expensive than bypass surgery. Heretofore, however, balloon angioplasty has not been considered as effective a treatment as bypass surgery. The effectiveness of balloon angioplasty, however, has improved significantly with the introduction of stenting, which involves the placement of a scaffold structure within an artery that has been treated by balloon angioplasty. The stent inhibits abrupt reclosure of the artery and has some benefit in inhibiting subsequent restenosis resulting from hyperplasia.
Presently available stents may be generally categorized as either “closed cell configurations” or “open cell configurations.” Closed cell configurations are characterized by ellipses, ovals, and polygonal structures, such as closed boxes, rhomboids, diamonds, and the like, which open in the circumferential direction and shorten in the axial direction as the stent is expanded. Open cell configurations include zigzag and serpentine structures which may be formed as a plurality of discreet rings or may be formed from a single continuous wire or other element. Closed cell stents are advantageous in that they provide better coverage of the blood vessel wall when the stent is deployed. This is particularly advantageous in tightly curved segments of the vasculature where even stent coverage in both the axial and circumferential directions on the outer wall of the vessel has been shown to reduce restenosis. Such even coverage is also an advantage in achieving uniform delivery from drug eluting stents. In contrast, open cell stent configurations are generally more flexible than the closed cell configurations. Such flexibility is advantageous in the tortuous regions of the vasculature where enhanced flexibility can provide better conformance to the vessel being treated. Better conformance can reduce the stress on the vessel wall, particularly at the stent ends, and lead to reduced restenosis.
For these reasons, it would be desirable to provide improved stents and stent structures. In particular, it would be desirable to provide stents and stent structures which combine the improved wall coverage of closed cell stent structures with the increased flexibility of open cell stent structures. It would be still further desirable if such improved stent structures allowed a physician to optimize the length of vessel being treated in accordance with the nature of the disease, allowed for the delivery of both very short and very long stent structures, and optionally permitted delivery of stent structures at multiple contiguous and/or non-contiguous locations within a body lumen. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. Pat. Nos. 6,200,337 and 5,870,381 describe stents having closed cell rings with overlapping portions connected by axial connecting members. U.S. Pat. No. 6,375,676 describes a stent having open cell rings with overlapping portions connected by axial connecting members. U.S. Patent Application Publication Nos. 2002/0188343 and 2002/0188347 describe expandable stents having interconnecting elements which interlock circumferentially adjacent bridges between axially adjacent stent segments. U.S. Pat. No. 4,580,568 describes the sequential placement of a plurality of zigzag ring stents where the stents may optionally be overlapped (FIGS. 7 and 8). U.S. Pat. No. 6,319,277 describes a stent formed from a single element into a plurality of nested “waves.” U.S. Pat. No. 5,554,181 describes a stent formed from a single element into partially overlapping windings. Other patents of interest include U.S. Pat. Nos. 6,312,458; 5,879,370; 5,755,776; 5,507,771; and 5,104,404. U.S. Pat. No. 6,258,117 B1 describes a stent having multiple sections connected by separable or frangible connecting regions. Optionally, the connecting regions are severed after the stent structure has been implanted in the blood vessel. U.S. Pat. Nos. 5,571,086; 5,776,141, and 6,143,016 describe an expandable sleeve for placement over a balloon catheter for the delivery of one or two stent structures to the vasculature. U.S. Pat. No. 5,697,948, describes a catheter for delivering stents covered by a sheath.